hi

Pros: Strong early & mid game.
Strut for Roaming and farming
AoE Ultimate
Get to pick her 99% of the time in ranked

Cons: No escape
Falls off during late game
Considered a terrible adc, so in low elo you will probably get flamed at if you don't do well
E is pretty much useless except at max rank, but is still pretty useless then

Miss Fortune is a lane bully so be aggressive but don't go too ham. Your easy harass combo is aaQaa. You basically want to hit your opponent when you don't have any creep to last hit and they are about to come in for one, and after you harass enough, you can zone.

Level 2
Miss Fortune has one of the strongest level 2s of all the adcarries, assuming you went Q>W. You will always want to try to pull the level 2 cheese, and if that works well, the lane is pretty much yours unless you mess up or the jungler gets you.

Q Bounce
This is SOOOO SOOOOOOOOO SOOOOOOOOOOOOOO IMPORTANT. Double Up < Just look at the damage a regular Q does, and the damage a second bounce Q does. Once you get good enough, the combo you want is aa Q(bounce off minion to champion) aa. It may sound stupid and hard now, but once you get it down laning phase will be a whole lot easier. Another reason why Q bounce is so important is that once you have a lead, the bounce does insane damage, and you can just zone your opponent with it.

You can play the mid game in two ways, depending on your preference and how well you are doing.

Split Pushing
This is my favorite way to play the role of adcarry in general. Miss Fortune has really great dueling potential if you build her well. You will generally only want to do this if you have good map awareness and you are strong enough to take on champions that will come after you while you split push. DO NOT do this if the enemy team has a fed assassin that you cannot fight against, because you will die and lose your lead eventually. Try to have your Statikk Shiv finished at this point so that you can push way faster and have insane tower clearing speed along with your W.

However, this is not exactly the same thing as Tryndamere or Shaco split pushing. You are still the ADC and you must rotate once you feel like a fight is coming up. If you are lower elo and your team will fight anytime they see enemies, you'll just have to anticipate when they'll fight and starting roaming to that place before the fight starts, or take 1-2 towers. You have the extra movement speed from Strut so roaming should be no problem.

Team Fighting
Miss Fortune is a great team fighter, and that's why most people pick her. Throughout early and mid game, and even late game if you build a Black Cleaver , you will be a major threat in all team fights with your ultimate. You generally want to stick with your teammates more often if you simply prefer to, or are not strong enough to be a threat while split pushing across other areas of the map. I will explain how to Team fight with her in later sections.

Positioning is the only thing that will keep you alive late game. You cannot afford to be caught out like Caitlyn or Tristana since they have an escape and you don't. Don't try to split push too far away from your teammates at this time of the game because that can cost you the game if you get caught. Just stick with your teammates but stay in a place where you won't get caught by key CC.

Banshee's Veil and Guardian Angel are the two main defensive items that adcarries get, I know that it may be YOLO risky to not get one of the two, but if you really need to carry your team and you see the opportunity to do so, opt for a Mercurial Scimitar Black Cleaver or Essence Reaver depending on you need and what kind of team you have.
Black Cleaver will especially keep your ult alive late game and the other two will keep your auto attacks relevant, while being able to break free from key abilities and sustaining.

But seriously, if a LeBlanc or another fed assassin is constantly deleting you every team fight, just get the Banshee's Veil and deal with the lower damage. What I'm saying is, if you fail to pressure the enemy team hard enough early - mid game and the game ends up late, you will need to take risks and not get a defensive item every game.

This is the only way I've thought of to keep up with the late game Vayne and Tristana as well as other hyper carries. Remember, if they don't opt for a 6th damage item, you'll be doing more damage than them, and if they do get a 6th damage item, you're putting that other adcarry at the same risk level as yourself, which is a good thing because it is better if you are both dead and doing no damage rather than you both being alive and doing damage, because a late game scaling adc will easily overpower you.

Ahead: If you get ahead, try to reach these numbers by the minute at the very least! Ideally you would be around ~280 cs by the 30 minute mark, but do not lose your team the game just to keep up with these milestones. Every game is different, and some games you will have only 180 by 30, and it is not your fault. It is only due the the pace of the game
10M - 70
20M - 150
30M - 250
Behind: If behind, try to reach these. IF you can, get Infinity Edge then Zeal or The Brutalizer and Avarice Blade. Do not finish Statikk Shiv or Youmuu's Ghostblade and just go on ahead farming creeps because you are behind. The Avarice Blade passive will help you catch up.
10M - 50-60
20M - 120
30M - 200-225

Once again, the chart is a mere guideline, do not religiously follow it.

Kills are never guaranteed, but minions are. Farming up alone will get you into high gold. An easy way to learn how to farm is by watching popular streams like Doublelift's or Wildturtle's. Look at where and why they are farming, their situations(including KDA), and theirs and enemy's team composition. Team composition does play a big role in determining how much farm you will get too.

Youmuu's Ghostblade - This item over shiv is mostly just preference. I put it in the "behind" build simply because if you are losing lane and don't have enough cash for bf or pickaxe on your first back, you can build 2 longswords with 720 gold and finish up ghostblade instead of going into shiv.

Trinity Force - Will help you kite and burst down opponents quickly. This item is not recommended if they have a tanky composition, as you should be going with Statikk Shiv

Black Cleaver - Only a good item if you have the team composition for it. You must land a good ult in team fights for this item to be more effective than going with an Essence Reaver or a Banshee's Veil

Key CC - Banshee's Veil
You don't have the best positioning
You cannot get away from somebody like malhpite
Thornmail is doing too much damage back to you. More lifesteal is another option if you don't need a defensive item
Skillshot magnet and can't dodge Thresh or Blitzcrank hooks
Siege
Instadeath - Guardian Angel
Somebody like Talon keeps getting you
No peel from your team
You have to go more ham than usual because everybody else on your team is behind with no damage

And other situational reasons

There are many combos she has to maximum her damage output, and here they are :)
1. aa Double Up (bounce) aa

When you're opponent is stunned/slowed/RIGHT NEXT TO YOU, do not just press R. If you have the opportunity during laning phase, do these to maximize damage

2. Impure Shots aa Double Up (bounce) Bullet Time
3. Impure Shots aa Double Up (bounce) aa(Only if the stun/slow is long enough) Bullet Time

Teamfights
4. Make it Rain Bullet Time aa whoever you can after that. You do that at the START of the fight. You are using your ultimate WHILE the enemy team are burning their cooldowns. You don't want to be autoattacking the enemy team when they all have their ultimate up! After your ult is done, stay in the range of 1 enemy champ at a time, and if you can try to position yourself with their squishies and kill them off(remember, ONLY IF YOU ARE IN THEIR RANGE ONLY ONLY ONLY) Don't throw the game to get a squishy down to 50% health.Burn Flash/Heal when somebody gets to you of course, and BORK, if you get it is another escape for you.

Once again, if you have any disagreements or questions, just leave me feedback. I will try to reply to all of them. I am aware that this guide is not completely organized right now, and that it needs a lot of work. I will get to that very...very soon. Thank you for viewing my guide!